In some medical systems, one or more elongate members may be implanted in a brain. For example, elongate members may be one or more leads that are implanted in a brain of a patient. For another example, elongate member may be a catheter or another therapeutic delivery device that delivers an agent to a brain. The elongate member may access regions of the brain through one or more burr holes formed through the patient's cranium. A burr cap assembly, which is positioned within a burr hole, may be used to retain the elongated medical device relative to the burr hole, as well as substantially plug an opening in the burr hole.